Recently, development of a solar cell using a single crystal silicon substrate actively proceeds.
In the related art, it has been known that a light-receiving surface of a solar cell using a single crystal silicon substrate has an optical confinement structure in which a front surface of the silicon substrate having the (100) plane is subjected to anisotropic etching, and thus a pyramid-like uneven shape is formed by the (111) surface. In such an optical confinement structure, because the pyramid-like uneven shape causes reflectivity of the front surface of the silicon substrate to be reduced, a short-circuit current can be increased.
A solar cell in which the front surface has the unevenness structure has diffusion type pn junction or hetero-junction type pn junction. In the diffusion type pn junction, conductive impurities are diffused in a silicon substrate. In the hetero-junction type pn junction, an amorphous silicon layer is formed on the front surface of a silicon substrate. As an electrode shape, a type in which electrodes are disposed on the front surface and the back surface of a silicon substrate, and a type in which electrodes are disposed only on the back surface of the silicon substrate are provided.
PTL 1: Japanese Unexamined Patent Application Publication No. 2012-195453